Producing, handling and storing bulk materials such as coal, ore, crushed rock, fertilizer, clay, grain and coke creates dust. Dust emissions add significant costs to mining, handling, and storing bulk materials such as coal, aggregate, and ore. Dust is noxious and can be dangerous if the material is flammable. There are many examples of coal and grain dust explosions that have taken lives and destroyed property. Dust is easily carried by the wind, creating toxic or unsightly conditions. Many handling operations have long recognized the fugitive dust problems and have imposed strict controls that can limit the capacity of a material handling facility.
Industry typically mitigates dust by applying water sprays at transfer points to agglomerate the dust. Costly chemicals such as foaming agents and surfactants may be added to the water to increase effectiveness. Numerous patents have been granted for specific dust suppression chemicals. For example, U.S. Pat. No. 5,310,494 (Method for controlling dusting of coke and coal, Bennett; Robert P., May 10, 1994) teaches that a foaming agent consisting of polyacrylate and lignosulfonate significantly reduces the amount of water required to control fugitive dust.
Traditional dust suppression methods have limited effectiveness for at least two reasons. First, dust created by friction and impact after the application may not be effectively controlled, so repeated applications may be required at each transfer point in the material handling process. Second, the water or chemical sprays evaporate, allowing dust to become airborne.
Water and chemical sprays dilute or contaminate the bulk material. For example, a small addition of 1 weight percent addition of water to coal will reduce its useful heating value by over 100 BTU/lb. Added water in cold weather creates ice that causes costly material handling problems.
Therefore, there remains a need in the art for improved methods of dust control that have greater effectiveness and avoid the problems associated with water and chemical sprays.